# US 4,840,519 A · Drill bit for hand drills > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,840,519 A - Document ID: US4840519A - Status: Granted - Kind: A - Application number: 07/065,944 - Filed: 1987-06-24 - Granted: 1989-06-20 - Earliest claimed: 1983-12-27 - Assignees: Gebruder Heller GmbH, Werkzeugfabrik - Inventors: Werner Kleine - Web page: https://patentgrep.com/patent/US4840519A ## CPC - B25D 17/088: {with radial movable locking elements co-operating with bit shafts specially adapted therefor} - B23B 31/005: {Cylindrical shanks of tools} - B23B 2231/0224: Rounded triangular - B23B 2231/0264: Axial grooves - B25D 2217/0034: Details of shank profiles - B25D 2217/0038: Locking members of special shape - Y10T 279/17042: Lost motion - Y10T 279/17615: Obliquely guided reciprocating jaws - Y10T 279/1986: Jaws - Y10T 408/907: including detailed shank - Y10T 408/953: Clamping jaws - B25D: PERCUSSIVE TOOLS {(percussive machines for forging B21J; hand-held drilling machines, in general B23B45/00, for wood B27C3/08; drilling machines, used for mining or quarrying, with reciprocating tool which is turned intermittently when out of contact with the working face E21B1/00)} - B23B: TURNING; BORING (arrangements for copying or controlling B23Q) - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract The invention contemplates an improved drill-bit construction wherein the shank by which the bit is clamped is characterized by (a) three angularly spaced grooves which are continuous over their entire length of engageability to the jaws of a multi-jaw chuck, (b) at least one of the grooves being closed at its rear end, (c) the rear end of the closed-end groove is at no greater offset than 5-mm from the rear end of the bit, and (d) the diameter of the cutting part of the bit shank is greater than the diameter of the clamping part of the shank, to an extent which at most results from shaped formation of the chip-removal groove. ## Claims ### Claim 1 A set of drill bits of different thickness, wherein each drill bit has a drill shank and a clamping shank which has a longitudinal axis and a circumferential surface, and wherein the circumferential surface of one drill bit is larger than the circumferential surface of another drill bit, the circumferential surface of each drill bit being interrupted by at least two angularly spaced and generally longitudinally extending grooves, each of said circumferential surfaces having at least one formation which adjoins each of said grooves, each said formation being a surface other than concentric about the longitudinal axis of the involved drill bit, and the sectional profile of each groove and its associated formation surface being identical for all drill bits of said set. ### Claim 2 A drill bit for hand drills, said bit having a drill shank and a clamping shank which has a longitudinal axis and a circumferential surface, said circumferential surface being interrupted by at least two angularly spaced and generally longitudinally extending grooves, each of said grooves being symmetrical about a geometric plane which includes said longitudinal axis, said circumferential surface having at least one formation which adjoins each of said grooves, said at least one formation for each groove being a surface which is cylindrical about an axis which is parallel to and eccentrically offset from said longitudinal axis and which is in the geometric plane of symmetry of the involved groove. ### Claim 3 A drill bit of metal for hand drills, said bit having a drill shank and a clamping shank which has a longitudinal axis and a generally circumferential surface which is characterized by displaced-metal formations, said circumferential surface being interrupted by at least two angularly spaced and generally longitudinally extending indented groove formations, said circumferential surface having at least one outwardly displaced formation which adjoins each of said grooves, said formations being surfaces which are other than cylindrical about said longitudinal axis, and at least one of said grooves terminating of the clamping shank end of said drill bit. ### Claim 4 (depends on 3) A drill bit according to claim 3, wherein each of said formation surfaces is an arcuate portion of a geometric cylinder having an axis parallel to but eccentrically offset from the longitudinal axis of the drill bit. ### Claim 5 (depends on 3, 4) A drill bit according to claim 3 or claim 4, wherein said clamping shank has an outer surface which is, at least in circumferentially distributed regions, cylindrical about the longitudinal axis of the drill bit, and wherein said formation surfaces extend radially beyond the geometrical cylinder of said regions. ### Claim 6 (depends on 2, 4) A drill bit according to claim 2 or claim 4, in which the number of said grooves is three. ### Claim 7 (depends on 2, 3) A drill bit according to claim 2 or claim 3, wherein the drill bit is one of a plurality of drill bits of different shank size, said grooves and adjoining formation surfaces being of the same plurality, angular spacing and local cross-section for each of the shank sizes of said plurality. ### Claim 8 (depends on 3) A drill bit according to claim 3, in which said formation surface is flat for each of said grooves. ### Claim 9 A set of drill bits of different thickness, wherein each bit has a drill shank and a clamping shank which has a longitudinal axis and a circumferential surface, and wherein the circumferential surface of one drill bit is larger than the circumferential surface of another drill bit, the circumferential surface of each drill bit being interrupted by at least two angularly spaced and generally longitudinally extending grooves, each of said grooves being symmetrical about a geometric plane which includes said longitudinal axis, each of said circumferential surfaces having at least one formation which adjoins each of said grooves, said at least one formation for each groove being a surface that is cylindrical about an axis (a) which is parallel to and eccentrically offset from the longitudinal axis of the involved drill bit and (b) which is in the geometric plane of symmetry of the involved groove, the radius of all said cylindrical formation surfaces being the same. ### Claim 10 (depends on 9) The drill bit of claim 9, wherein the number of cylindrical-surface formations for each groove is two. ### Claim 11 A set of hand-drill bits of metal of different thickness, wherein each drill bit has a drill shank and a clamping shank which has a longitudinal axis and a generally circumferential surface which is characterized by displaced metal formations, and wherein the circumferential surface of one drill bit is larger than the circumferential surface of another drill bit, the circumferential surface of each drill bit being interrupted by at least two angularly spaced and generally longitudinally extending indented groove formations, each of said circumferential surfaces having outwardly displaced formations which adjoin each of said grooves, said formations for each groove being surfaces other than cylindrical about said longitudinal axis, the sectional profile of each groove and its associated formation surfaces being identical for all drill bits of said set, and at least one of said grooves of each drill bit terminating short of the clamping-shank end of the involved drill bit. ### Claim 12 (depends on 11) A drill-bit set according to claim 11, in which said surfaces of said formations are flat. ### Claim 13 (depends on 1, 9, 11) A drill-bit set according to claim 1 or claim 9 or claim 11, in which the number of grooves in each drill bit is three.